In adult farm workers, pesticide exposure is associated with cognitive deficits. Whether exposure to pesticide causes impairments and declines in specific cognitive domains beyond what would be expected due to normal aging alone is not known. Normal aging is associated with declines in various complex cognitive abilities, including declines in processing speed, working memory, mental flexibility, and spatial learning, while some aspects of cognition, such as those involving verbal skills, implicit learning, and semantic memory, generally remain largely spared. Poor complex cognitive abilities are associated with greater limitations in activities of daily living, problems accessing health care systems, vulnerability to disease, injury, malnutrition, and subsequently a loss of ability to function independently in the community. That loss of independence impairs the quality of life for both the affected individuals and their caregivers, and constitutes a major financial burden to affected families and society. Previous studies suggest that exposure to pesticide is associated with the risk for cognitive impairment, but no study has examined whether low-level chronic exposure to pesticide exacerbates age-related impairments in cognitive function. Distinguishing cognitive decrements associated with pesticide exposure from normal aging could prove to be a sensitive measure of the effects of low-level chronic exposure to pesticide. We propose an exploratory project to document the effects of pesticides on cognitive function in older adults. This study will enable us to address the following aims. The primary aims are (1) to identify the domains of cognitive function that are affected by pesticide exposure; and (2) to determine whether older farm workers are more vulnerable to the effects of pesticide exposure and have significantly poorer cognitive scores than younger farm workers. A secondary aim focuses on exploring the relative contributions of normal aging and pesticide exposure to change in cognitive function at 1-year follow-up. Our goals are to provide an early understanding of the interaction of aging and pesticide exposure on cognitive function, and to achieve exploratory longitudinal study benchmarks, including quality control, recruitment, retention, measures refinement, and sample size estimates. The information will provide the foundation for future definitive studies directed towards identifying and characterizing cognitive domains that are affected and temporal decline in cognitive function as related to pesticide exposure.